In typical axial flow compressors in gas turbine engines, an annular airflow channel of progressively decreasing area is defined between a compressor case and a rotor in the case. Annular rotor blade stages motivate flow in the airflow channel and annular stator vane stages between the rotor blade stages redirect the airflow. In variable geometry axial flow compressors, the stator vanes are rotatable about spoke-like radial axes of the case. A hub-like shroud ring on the radially inner ends of the stator vanes defines the inner boundary of the airflow channel where it traverses the stator vane stage and supports seals which minimize leakage. In split-case axial flow compressors of fixed or variable geometry, where the case is split in a horizontal center-plane of the compressor for assembly purposes, the shroud ring is likewise split into a pair of 180-degree arc shroud ring segments.
Many arrangements have been proposed for attaching shroud ring segments to stator vanes in split-case, axial flow compressors. In a fixed geometry proposal, a pair unitary or one piece 180-degree arc shroud ring segments are attached to the stator vanes through hook-like projections on the inner ends of the vanes which seat in individual sockets in the unitary, shroud ring segments. In some prior variable geometry proposals, short arc-shaped shroud ring segments are assembled with corresponding groups of vanes and then unitized into 180-degree arc segments by end plates or like connecting devices. In other prior variable geometry proposals, 180-degree arc shroud ring segments are formed by bolting together two 180-degree arc end pieces. In the latter proposals, inner buttons or projections of the vanes are rotatably sandwiched between the bolted-together end pieces. While the bolted-together proposals do not require as many individual pieces as the multi-segment proposals, they are limited to relatively large compressors because the diameters of the shroud ring segments must be large enough to accommodate both the inner vane buttons and the bolts or other fasteners holding the end pieces together. A stator vane stage and method of making the same according to this invention features unitary or one-piece 180-degree arc shroud ring segments rotatably connected to variable geometry stator vanes.